A method and a device for the photothermic investigation of a sample are known, for example, from the brochure “LFA 447 Nano Flash” from Netzsch-Gerätebau GmbH, Selb, Germany (downloadable on Jul. 4, 2012 on the Internet at http://netzsch-thermal-analysis.com/download/LFA_447_NanoFlash_D_1108_de_180.pdf). The known device comprises:                a sample chamber in the form of an electrically operated oven with a sample holder accommodated therein for the arrangement and temperature control of the sample,        a xenon flash lamp as excitation source for generating an excitation beam directed onto a front side, which functions as an “excitation side”, of the sample to be investigated, and        an infrared detector for detecting thermal radiation emitted from a “detection side”, here the rear side of the sample.        
A device and a method for the photothermic investigation of a sample is known from DE 10 2012 106 955 B4. In the case of this prior art, provision is made between the sample holder and the detector for an adjustable detecting lens, which can be adjusted in such a manner for setting a desired field of vision of the detector on the sample surface.
Physical characteristics of the material of the sample, such as in particular the temperature conductivity thereof, as well as the heat conductivity thereof, can be determined by means of the known device. With the knowledge of the density of the respective material, the specific thermal capacity of the material can also be determined.
It is the operating principle of the known device to irradiate a first side (“front side”) of the sample with a short electromagnetic excitation pulse by means of the excitation source, to then detect a thermal radiation emitted from a second side (“rear side”) of the sample located opposite the first side (as a measure for the temperature on the second side), as a result of the excitation pulse, and to finally evaluate the detected thermal radiation on the basis of a physical-mathematical model, so as to determine the mentioned material parameters (as the corresponding model parameters, which are estimated in response to the equalizing calculation) by means of a mathematical equalizing calculation.
The ability to control the temperature of the sample chamber optionally provides for such measurements either at a predetermined certain sample temperature, or across a larger temperature range (in that the temperature is changed in small steps, e.g., and a corresponding plurality of individual measurements is carried out).
Such a photothermic investigation works well for opaque samples, that is, without a larger permeability of the sample material for the thermal radiation created on the surfaces or (also) in the interior of the sample, respectively.
However, the investigation of more or less transparent samples is problematic, because the models resulting from physical-mathematical considerations in this case become relatively complex, in particular include numerous model parameters, which must be estimated in the equalizing calculation, so that the accuracy of the determination of the material parameters, which are ultimately of interest, such as in particular temperature conductivity and/or heat conductivity, e.g., suffers from this.